Altitude-instrument



2 Sheets-Sheet 1.

(No Model.)

s. 0. CHANDLER, Jr.

Altitude Instrument.-

No. 239,315. PatentedfMarch 29,1881.

WITN 55555 INVENTU N. PETER; PHOTOLITHOGRAFMER, WASHINGTON. D C.

(No Model.) 2 SheetS-SheetZ.

s. (L'OHANDLER, J r. Altitude Instrument.

No. 239,315; Patented March 29,1881.

WITNESSES V IN ENTEI ".PEYERS, FHamLrmwmPnEn, WASHINGTON, c. c.

U ITED STATES PATENT OFFICE.

SETH O. CHANDLER, JR, OF BOSTON, MASSACHUSETTS.

ALTITUDE-INSTRUM ENT..

SPECIFICATION forming part of Letters Patent No. 239,315, dated March29, 1881.

Application filed April 23, 1880.

To all whom it may concern:

Be it known that I, SETH G. CHANDLER,

. Jr., of Boston, in the county of Suflolk and State of Massachusetts,have invented a new and useful Instrumentfor Measuring Equal Altitudes,of which the following is a specification.

The nature of my invention consists in attaching to a swinging bar asmall telescope and an adjustable reflector, the telescope beingprovided with a spider-line diaphragm, which is placed, as usual, in thefocus of the eye-piece.

My invention also consists in combining with the swinging telescope andreflector certain devices and modifications, which may be bestunderstood by reference to the drawings and specification.

In the drawings, Figure l is an elevation of my invention. Fig. 2 is avertical section of the same.- Fig. 3 is an enlarged section, showingthe method of suspending the swinging rod. Fig. 4 is a plan of thedevice for suspending the swinging rod, the cap being represented as cutoff at the line as y, Fig. 3. Fig.

5 is a diagram to show the principle of action of my invention.

The outer case of my instrument is indicated by the letters A A B, Figs.1 and 2. At the upper end of the tube A, I affix a cap, A (See Fig. 3.)On the under side of the cap A I attach a cross-bar, H. (See Figs. 3 and4.) This cross-bar H has a pointed pin or stud, K, projecting upwardfrom its center. Upon the point of the stud K, I suspend a piece ofmetal, D D, the shape of which is shown in Figs. 3 and 4, the part Dbeing annular, and serves to support the eyepiece tube L. The otherpart, D has upon its underside an indentation, in which the point of thestud K works; and to this part D", I fasten the rod D.

The part designated by D D which I will hereinafter call thesupporting-ring, is free to swing in all directions but it cannot turnon its vertical axis, it being checked by the small projecting pin E,which plays between the two guides E E, Figs. 3 and 4.

The rod D has attached to its lower end a weight, D, (see Fig. 2,) whichserves to main (No model.)

tain it in a constant position in relation to the vertical. To this rodD, I attach the objectglass L and the adjustable reflector M.

All of the parts of the instrument that are depended upon for detectingequal altitudes namely, the eye piece L", the spider-line diaphragm L,the object lens L and the reflector M--are connected to and governed bythe weighted rod D, (see Figs. 2 and 5,) and are thus free to adjustthemselves into a constant position in relation to the vertical.

The tubes A and B serve simply as a support and covering for the otherparts. upper part of the tube B colored or darkened glasses may beplaced to shield the eye from the sun when solar observations are taken.

To use this instrument for obtaining true time by the sun, theinstrument is adjusted to show the passage of the image of the sun onthe reflector M, the exact chronometer time of the passage across thespider-lines being observed, the reflector being firmly fixed in itsadjusted position in relation to the rod D. This constitutes the firstobservation, and is to be taken before meridian passage of the bodyobserved. The second observation is to be taken after meridian'passage.This is to be recorded in the exact chronometer time.- The mean time ofthe two observations will give exact time (by chronometer) of thepassage of the body across the meridian, and by an ordinary calculation,with the aid of an ephemeris, the exact error of the chronometer may beascertained.

If desirable, the device may be inverted and the image thrown onto ascreen, the screen being attached to the same swinging bar that theother parts are.

Having thus described my invention, what I desire to secure by LettersPatent is- In an altitude-instrument, the combination of a pendulumhaving upon it a light-directing device with an eye-piece and definingIn the r line or lines, substantially as described, and I for thepurpose set forth. SETH O. CHANDLER, JR.

Witnesses:

HELEN M. FEEGAN, WM. S. SAMPSON.

